.app{
    width: 100%;
    height: 100vh;
    position: relative;
    display: flex;
    justify-content: center;
    align-items: center;
}
button{
	width: 140px;
	height: 46px;
	font-size: 16px;
	font-family: Arial, Helvetica, sans-serif;
	font-weight: 700;
	color: #333;
	background-color: transparent;
	border: none;
	position: relative;
	box-sizing: border-box;
	transition: all 0.4s ease-in-out;
}
button:before{
	content: '';
	width: 4px;
	height: inherit;
	position: absolute;
	top: 0;
	left: 0;
	z-index: -5;
	background-color: #333;
	transition: all 0.4s ease-in-out;
}
button:hover{
	cursor: pointer;
	color: #fff;
}
button:hover:before{
	width: 100%;
	border-radius: 6px;
}